This invention relates to a process for filling a muffler shell with fibrous material, and a muffler shell filled with fibrous material.
U.S. Pat. No. 4,569,471 to Ingemansson et al. describes a process and apparatus for feeding lengths of a continuous glass fiber strand into a muffler outer shell. The apparatus includes a texturizing device with a nozzle for expanding the fiber strand into a wool-like material before the material enters the outer shell. In a first embodiment, filling of an outer cylinder 14 of the muffler shell occurs without an end-piece joined to the outer cylinder 14. After the filling operation is completed, the outer cylinder 14 is moved to a separate station where the end piece is welded onto the outer cylinder 14. In a second embodiment, illustrated in FIG. 3, a perforated pipe/outer end piece assembly is located only part way in the muffler outer cylinder 14 during the glass material filling operation. After the filling operation has been completed, the perforated pipe/end piece assembly is moved to its final position within the outer cylinder 14.
The ""471 patent process is typically not used with clam shell mufflers comprising first and second halves which, when coupled together and enclosing a perforated pipe, may not have an open end through which fibrous material may be fed.
It is also known in the prior art to form preforms from glass material which are adapted to be inserted into a first muffler shell section prior to it being coupled to a corresponding second shell section; see U.S. Pat. No. 5,766,541, the disclosure of which is incorporated herein by reference. While such preforms are acceptable in performance, they add additional cost to the muffler due to the manufacturing steps necessary to form the preforms.
It is also known to fill bags or a mesh with fibrous material. The filled bag or mesh is then inserted into a first muffler shell section prior to the first shell section being coupled to a second shell section, see U.S. Pat. No. 6,068,082, the disclosure of which is incorporated herein by reference. However, assembly of such mufflers is oftentimes difficult and time consuming due to the expanded nature of the filled bag and limited volume within the muffler shell outer parts. It is noted that any fibrous material extending out beyond the outer edges of the first and second muffler shell outer parts may have a detrimental impact on a weld at that point, i.e., may cause a void in the weld, and exposed fibers are aesthetically undesirable.
Hence, there is a need for an improved, low-cost muffler outer shell filling process which can be used to fill muffler shells.
In accordance with a first aspect of the present invention, a process is provided for filling a muffler shell with fibrous material. The process comprises the steps of: providing a muffler shell comprising one or more muffler shell outer parts which define an internal cavity and an internal structure adapted to extend at least part way through the shell internal cavity and having one or more openings adapted to communicate with the shell internal cavity; providing a bag filled with fibrous material, the bag having a first side with one or more first perforations defining a first side total open area and a second side with either no perforations or one or more second perforations defining a second side total open area, the first open area being greater than the second open area; positioning the fibrous material-filled bag adjacent the internal structure such that the first side is nearest to the internal structure; and drawing a partial vacuum through the internal structure, the partial vacuum drawing the fibrous-filled bag inwardly towards the internal structure.
The partial vacuum may be drawn prior to or at about the same time as the occurrence of the positioning step. The partial vacuum may also be drawn subsequent to the positioning step.
The muffler shell may comprise first and second muffler shell outer parts. The process may further comprise the steps of: placing the internal structure in the first muffler shell outer part subsequent to the positioning step and while the partial vacuum is being drawn through the internal structure; placing the second muffler shell outer part adjacent to the first muffler shell outer part while the partial vacuum is still being drawn through the internal structure such that the first and second muffler shell parts define an internal cavity containing the internal structure, and the fibrous material-filled bag; and joining the first and second muffler shell parts to one another. Alternatively, the process may further comprise the steps of: placing the internal structure in the first muffler shell outer part prior to the positioning step; placing the second muffler shell outer part adjacent to the first muffler shell outer part subsequent to the positioning step such that the first and second muffler shell parts define an internal cavity containing the internal structure, and the fibrous material-filled bag; and joining the first and second muffler shell parts to one another.
The fibrous material in the bag may comprise a mineral fiber wool-type product.
The step of drawing a partial vacuum through the internal structure may comprise the step of connecting a vacuum source to the internal structure.
The bag may be formed from paper, cardboard, fiberglass, a polymeric material or any other suitable material.
The internal structure may comprise at least one perforated element such as a perforated pipe.
The first side total open area may comprise between about 1% and about 60% of the total surface area of the first side of the bag and the second side total open area may comprise between about 0% and about 4% of the total surface area of the second side of the bag. Accordingly, between about 40% and about 99% of the total surface area of the first side of the bag comprises a solid, non-open area and is defined by the material from which the bag is formed and between about 96% and about 100% of the total surface area of the second side of the bag comprises a solid, non-open area and is defined by the bag material. Hence, the xe2x80x9ctotal surface areaxe2x80x9d of the first side of the bag includes open and non-open areas and the xe2x80x9ctotal surface areaxe2x80x9d of the second side of the bag includes open and non-open areas.
The muffler shell may alternatively comprise a generally cylindrical main shell portion and opposing end caps. One of the end caps may be integral with the main shell portion or the internal structure, while the other end cap is adapted to be coupled such as by welding or crimping to the cylindrical main shell portion. Alternatively, both end caps may be formed as separate parts from the main shell portion. The method may further comprise the step of placing the internal structure in the generally cylindrical main shell portion subsequent to the positioning step and while the partial vacuum is being drawn through the internal structure.
In accordance with a second aspect of the present invention, a muffler is provided comprising a muffler shell including one or more muffler shell outer parts which define an internal cavity; an internal structure adapted to extend at least part way through the shell internal cavity and having one or more openings communicating with the shell internal cavity; and a fibrous-filled bag positioned in the internal cavity, the bag having a first side with one or more first perforations defining a first side total open area and a second side with either no perforations or one or more second perforations defining a second side total open area, the first open area being greater than the second open area.
The internal structure may comprise at least one perforated element.
The fibrous material may comprise a mineral fiber wool-type product.
The first side total open area may comprise between about 1% to about 60% of the first side of the bag and all ranges subsumed therein and the second side total open area may comprise between about 0% to about 4% of the second side of the bag, all ranges subsumed therein, and preferably between about 0% to about 0.5% of the second side of the bag.
Advantages associated with the present invention include: improved bag placement within the internal cavity due to the creation of a partial vacuum in the internal structure; reduction in time required to fill a muffler shell with fibrous material; muffler shell filling may occur without tape to maintain a fibrous material-filled bag in position within the muffler shell or a texturizing device if the bags to be placed within the muffler shell have been previously filled with fibrous material; improved muffler acoustic attenuation properties due to proper location and compaction of the fibrous material around and against the internal structure.